Read THIS absurdly long thread and come to your own conclusions 
Personally my rule is:
Teaming tank who can handle aggro well - pick up taunt as a priority
Teaming tank who can't handle aggro well - pick up taunt, but not as a priority
Soloing tank - don't pick up taunt
Soloing tank who I'll be PvPing with - pick up taunt, but not as a priority
Defiant 50�s: Generalissimo, Righteous Bob, Splortch, Brutus Cayuga
Union 50's: Chimera Obscura, Diet Anthracite, Grim Proctologist, Puny Little Minion, Raging Bitumen
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For the type of tank and type of tanking you will do, I would pick up taunt.
UNION
Officer Cuffz lvl 50 Inv/Nrg Tank
Badge lvl 50 dwarf/human Peacebringer
Dark Air lvl 50 Ice/Cold Corruptor
Ayre lvl 50 Storm/Elec Defender
Total Cat: @Officer Cuffz
"When I say interview, I mean engage in combat and defeat..." -Laura Brunetti, on how to deal with Warriors.
You've got Chilling Embrace, which is a fantastic taunt tool. Getting Taunt shouldn't be a priority, but it depends a bit on your playstyle.
I like Taunt, I find I use it often and saves me to run left and right to pick agro.
On the other hand I was toying with the idea of maxing the defenses (at least using the planner) I can reach the 45% cap.
But for this I need Weave, and I already have Tough, this means I had to fit in Stamina despite EA since I'm playing Staminaless right now but it's a fine line which another power hungry toggle would not help.
I managed to fit it all but at the expense of Icicles which I find I quite like, being always surrounded by enemies and ticking an average of 10-12 seems pretty good.
Trouble is, all powers are counted (though only to level 38, I suppose I could fit it beyond but I'd rather have it now than who knows when (level 31 at the moment)) and to fit in Icicles only Taunt is dispensable.
So, to Taunt or not to Taunt?
The build is :
01) --> Frozen Armor==> EndRdx(1) DefBuf(3) DefBuf(3) DefBuf(5)
01) --> Scorch==> Acc(1)
02) --> Hoarfrost==> Rechg(2) Rechg(5) Rechg(11) Heal(13) Heal(13) Heal(15)
04) --> Chilling Embrace==> EndRdx(4) Taunt(15)
06) --> Combustion==> Acc(6) Acc(7) Dmg(7) Dmg(9) Dmg(9) Rechg(11)
08) --> Wet Ice==> EndRdx(8)
10) --> Combat Jumping==> DefBuf(10) DefBuf(17) DefBuf(17) EndRdx(21)
12) --> Boxing==> EndRdx(12)
14) --> Super Jump==> Jump(14) Jump(37)
16) --> Swift==> Run(16)
18) --> Glacial Armor==> EndRdx(18) DefBuf(19) DefBuf(19) DefBuf(21)
20) --> Tough==> DmgRes(20) DmgRes(23) DmgRes(23) EndRdx(25)
22) --> Health==> Heal(22) Heal(25) Heal(34)
24) --> Taunt==> Rechg(24)
26) --> Energy Absorbtion==> Rechg(26) Rechg(27) Rechg(27) EndMod(36) EndMod(37) EndMod(37)
28) --> Fire Sword Circle==> Acc(28) Acc(29) Dmg(29) Dmg(31) Dmg(31) Rechg(31)
30) --> Weave==> DefBuf(30) DefBuf(33) DefBuf(34) EndRdx(34)
32) --> Hibernate==> Rechg(32) Rechg(33) Rechg(33)
35) --> Stamina==> EndMod(35) EndMod(36) EndMod(36)
38) --> Greater Fire Sword==> Acc(38) Acc(39) Dmg(39) Dmg(39) Dmg(40) Rechg(40)